<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8" />
    <title>title</title>
    <style>
        #result {
            display: flex;
            justify-content: center;
            color: #ec181e;
            font-size: 25vw;
            font-weight: 900;
            text-shadow: 0 6ox 4px rgba(255, 100, 100, 0.6);
        }
    </style>
</head>

<body>
    <div id="result">00:00:00</div>
    <script>
        //execute startTimer() once every 1 second
        var intervalID = setInterval(startTimer, 1000)

        function startTimer() {
            var date = new Date();
            var x = document.getElementById("result");
            x.innerHTML = date.getHours() + ":" + date.getMinutes() + ":" + date.getSeconds();
        }
    </script>
</body>

</html>